Burst Capacitor

I feel that the capacitor might have an oil-impregnated paper dielectric. May be there was a short circuit inside the capacitor bank and the oil burnt and expanded. The pressure increases and the capacitor bursts.

To avaoid this, capacitors should have a PRD (Pressure Relief Device) in built.

Very good possibility. Also if the cap was installed recently it may have been installed backwards.

Check Badcaps.net for the best advice on capacitors.http://www.badcaps.net They have a nice forum for more help.

Check the manufacturer's spec on ambient heat range. Some caps WILL explode if the heat goes over 60-65 deg Celsius. If it's on a PFC installation you may be getting a heat build up from the resistors in your setup that is exceeding specifications. Run a temp logger for a few days and check the results. Try to keep it below 45 deg C with thermostat initiated fans with an alarm to caution high temp. We always designed a trip out of the PFC's at 50Deg C to avoid any jelling and deformation which could lead to shorts and ... explosions.

Among the possibilities are:

• Overvoltage
• Dielectric breakdown
• Mechanical damage
• Sabotage
• Lightning strike
• etc.

I would add harmonics currents overloading and lightening surges.

Those type of capacitors have a working life.

Then they must be replaced before they totally pissed off.

The life shortens with the ambient temperature, of which ionisate the insulation oil inside, of which changing the dielectric value.

Therefore if the capacity is decreased in % 10, of it's rating value, then it is logical to replace it with the new one.

The easiest way to check this by using a clamp meter, and compare the actual current with the rated current of the capacitor. (Do this at least once a month for all the capacitors in the capacitor bank and make a spreadsheet. )

Remember "If you don't measure, you cannot control."

Kindest Regards.

probability of natural mortillity of components.

Had a number of capacitors in the panel bursted simultaneously then can be sorted for a problem.

Failure of a single out of a battch is not a problem of that sort.